SUBROUTINE DORG2R( M, N, K, A, LDA, TAU, WORK, INFO ) 2,3
!
!  -- LAPACK routine (version 3.1) --
!     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
!     November 2006
!
!     .. Scalar Arguments ..
      INTEGER            INFO, K, LDA, M, N
!     ..
!     .. Array Arguments ..
      DOUBLE PRECISION   A( LDA, * ), TAU( * ), WORK( * )
!     ..
!
!  Purpose
!  =======
!
!  DORG2R generates an m by n real matrix Q with orthonormal columns,
!  which is defined as the first n columns of a product of k elementary
!  reflectors of order m
!
!        Q  =  H(1) H(2) . . . H(k)
!
!  as returned by DGEQRF.
!
!  Arguments
!  =========
!
!  M       (input) INTEGER
!          The number of rows of the matrix Q. M >= 0.
!
!  N       (input) INTEGER
!          The number of columns of the matrix Q. M >= N >= 0.
!
!  K       (input) INTEGER
!          The number of elementary reflectors whose product defines the
!          matrix Q. N >= K >= 0.
!
!  A       (input/output) DOUBLE PRECISION array, dimension (LDA,N)
!          On entry, the i-th column must contain the vector which
!          defines the elementary reflector H(i), for i = 1,2,...,k, as
!          returned by DGEQRF in the first k columns of its array
!          argument A.
!          On exit, the m-by-n matrix Q.
!
!  LDA     (input) INTEGER
!          The first dimension of the array A. LDA >= max(1,M).
!
!  TAU     (input) DOUBLE PRECISION array, dimension (K)
!          TAU(i) must contain the scalar factor of the elementary
!          reflector H(i), as returned by DGEQRF.
!
!  WORK    (workspace) DOUBLE PRECISION array, dimension (N)
!
!  INFO    (output) INTEGER
!          = 0: successful exit
!          < 0: if INFO = -i, the i-th argument has an illegal value
!
!  =====================================================================
!
!     .. Parameters ..
      DOUBLE PRECISION   ONE, ZERO
      PARAMETER          ( ONE = 1.0D+0, ZERO = 0.0D+0 )
!     ..
!     .. Local Scalars ..
      INTEGER            I, J, L
!     ..
!     .. External Subroutines ..
!     EXTERNAL           DLARF, DSCAL, XERBLA
!     ..
!     .. Intrinsic Functions ..
      INTRINSIC          MAX
!     ..
!     .. Executable Statements ..
!
!     Test the input arguments
!
      INFO = 0
      IF( M.LT.0 ) THEN
         INFO = -1
      ELSE IF( N.LT.0 .OR. N.GT.M ) THEN
         INFO = -2
      ELSE IF( K.LT.0 .OR. K.GT.N ) THEN
         INFO = -3
      ELSE IF( LDA.LT.MAX( 1, M ) ) THEN
         INFO = -5
      END IF
      IF( INFO.NE.0 ) THEN
         CALL XERBLA( 'DORG2R', -INFO )
         RETURN
      END IF
!
!     Quick return if possible
!
      IF( N.LE.0 ) &
         RETURN
!
!     Initialise columns k+1:n to columns of the unit matrix
!
      DO 20 J = K + 1, N
         DO 10 L = 1, M
            A( L, J ) = ZERO
   10    CONTINUE
         A( J, J ) = ONE
   20 CONTINUE
!
      DO 40 I = K, 1, -1
!
!        Apply H(i) to A(i:m,i:n) from the left
!
         IF( I.LT.N ) THEN
            A( I, I ) = ONE
            CALL DLARF( 'Left', M-I+1, N-I, A( I, I ), 1, TAU( I ), &
                        A( I, I+1 ), LDA, WORK )
         END IF
         IF( I.LT.M ) &
            CALL DSCAL( M-I, -TAU( I ), A( I+1, I ), 1 )
         A( I, I ) = ONE - TAU( I )
!
!        Set A(1:i-1,i) to zero
!
         DO 30 L = 1, I - 1
            A( L, I ) = ZERO
   30    CONTINUE
   40 CONTINUE
      RETURN
!
!     End of DORG2R
!
      END SUBROUTINE DORG2R